menu.header.image.unacom.logo
 

National Committee on Marine Sciences (NCMS)

Permanent URI for this communityhttps://repository.unesco.gov.ph/handle/123456789/6

Browse

Filters

Settings

AGROVOC Keyword: search.filters.agrovoc.phosphates

Search Results

Now showing 1 - 4 of 4
  • No Thumbnail Available
    Ammonium and phosphate excretion in three common echinoderms from Philippine coral reefs
    Dy, Danilo T.; Yap, Helen T. (Elsevier BV, 2000-08)
    The ammonium and phosphate excretion and oxygen consumption of three species of echinoderms (Tripneustes gratilla, Protoreaster nodosus and Ophiorachna incrassata) commonly encountered in Philippine coral reefs were investigated in relation to time of day (i.e. daytime between 10:00 and 12:00 h vs. nighttime between 22:00 and 24:00 h) and their recent feeding history (i.e. recently-collected vs. short-term starvation for 3±1 days). The experiment used whole organism incubations and followed a nested hierarchical design. Ammonium excretion rates were 1447±310 nmol g−1 DW h−1 (mean±S.E., n=24) for T. gratilla, 361±33 for O. incrassata and 492±38 for P. nodosus. Ammonium excretion differed significantly among species, time of incubation and recent feeding history. Interaction between species and recent feeding history was also significant. The organisms excreted more ammonium during daytime except for starved specimens of O. incrassata. In addition, animals that were starved in the laboratory for a few days had a tendency to excrete more ammonium than recently-collected specimens. Phosphate excretion rates were 25±13 nmol g−1 DW h−1 for T. gratilla, 10±2 for O. incrassata and 4±1 for P. nodosus. There were no significant differences in phosphate excretion among the three species of echinoderms, their recent feeding history and time of day. Oxygen consumption rates were 286±24 μg O2 g−1 DW h−1 for T. gratilla, 64±3 for O. incrassata and 54±3 for P. nodosus. Oxygen consumption differed significantly among species and recent feeding history but differed only slightly with time of incubation. There was a significant correlation between oxygen consumption and ammonium excretion (r=0.48, P=0.018), and between oxygen consumption and phosphate excretion (r=0.41, P=0.047) for T. gratilla. The nutrient excretion by tropical echinoderms is another pathway by which inorganic nutrients are regenerated in coral reef communities. However, the quantity of nutrients excreted is dependent on the species of echinoderms, their nutritional status and time of day.
  • No Thumbnail Available
    Growth and metabolic responses of the giant clam-zooxanthellae symbiosis in a reef-fertilisation experiment
    Belda-Baillie, C. A.; Leggat, W.; Yellowlees, D. (Inter-Research Science Center, 1998)
    To evaluate the impact of elevated nutrients on reef organisms symbiotic with zooxanthellae, giant clams Tridacna maxima were exposed daily to increased ammonia and phosphate (N, P, N+P) in their natural reef environment for 3 to 6 mo. The results strongly corroborate the major responses of the symbiotic association to nutrient enrichment previously observed (with T. gigas) under controlled outdoor conditions. Exposure of the clams to elevated N (10 µM) increased zooxanthellae density, reduced zooxanthellae size, down-regulated N uptake by zooxanthellae freshly isolated from their hosts, and reduced glutamate in the clam haemolymph, with increased pools of some free amino acids (methionine, tyrosine) in the zooxanthellae. These results confirm that the zooxanthellae in giant clams are N limited in situ and have free access to inorganic N from the sea water. There is also corroborating evidence that the zooxanthellae are P limited in situ as well, possibly due to host interference. While the N:P ratios of the animal host reflected ambient N and P concentrations in the sea water, those of the zooxanthellae did not. Regardless of P exposure (2 µM P) of the clams, zooxanthellae N:P ratios were consistently high(>30:1) and phosphate concentrations in the clam haemolymph bathing the zooxanthellae tube system consistently low (<0.1 µM). These field findings, consistent with previous laboratory observations, confirm the limiting roles of both N and P in the giant clam-zooxanthellae symbiosis. That significant changes occurred earlier and at lower nutrient loading compared to some reef organisms investigated within the same experimental framework further demonstrates organism-level responses of a potential bio-indicator of the early onset of eutrophication in reef waters.
  • No Thumbnail Available
    Phosphate acquisition in the giant clam-zooxanthellae symbiosis
    Belda, C. A.; Yellowlees, D. (Springer, 1995-12)
    The effect of phosphate on the giant clam Tridacna gigas and on its symbiotic dinoflagellate Symbiodinium sp. was compared with that on cultured Symbiodinium sp. originally isolated from the same clarn species. Incubation of whole clams in elevated phosphate (10 μM) reduced their capacity for phosphate uptake, but the uptake capacity of the clam's zooxanthellae population was not influenced. In addition, there was no change in the zooxanthellae density and the N:P ratio, of these algae. On the other hand, cultured zooxanthellae were influenced by the phosphate regimen of their culture medium. Compared with controls (0 μM P), addition of 10 μM phosphate to the culture medium caused an increase of 100% in cell density and decreases of 50% in the N:P ratio, and 80% in the phosphate-uptake capacity of the zooxanthellae. Zooxanthellae freshly isolated from the clams exhibited properties similar to those of zooxanthellae cultured in the absence of phosphate. These results demonstrate that the zooxanthellae population of T. gigas have limited access to the inorganic phosphate in sea water and the phosphate reserves within the animal host.
  • No Thumbnail Available
    Nitrate and phosphate uptake of morphologically distinct calcified macroalgae
    Narvarte, Bienson Ceasar V.; Hinaloc, Lourie Ann R.; Gonzaga, Shienna Mae C.; Crisostomo, Bea A.; Genovia, Tom Gerald T.; Roleda, Michael Y. (Informa UK Limited, 2023-05-02)
    Calcified macroalgae are essential components of marine ecosystem, yet much of their physiology remains to be understood. Here, the nutrient (NO3– and PO4–3) uptake physiologies of two branched macroalgae, Actinotrichia fragilis (Nemaliophycidae) and Amphiroa fragilissima (Corallinophycidae), and the non-geniculate rhodolith Sporolithon sp. (Corallinophycidae) were examined. Sporolithon sp. had the lowest uptake rate through time and the three calcified macroalgae had a surge in NO3– and PO4–3 uptake that occurred between 3 and 20 min, with a maximum uptake at 3 min, after which the nutrient uptake rates declined. The NO3– uptake of the three calcified macroalgae followed Michaelis-Menten kinetics. For NO3– uptake, Sporolithon sp. had the lowest Km (2.72 ± 0.97 µM), Vmax (0.08 ± 0.01 µmol gDW–1 h–1), Vmax/Km (0.05 ± 0.03 µmol gDW–1 h–1 µM−1) and α (0.01 ± 0.00 µmol gDW–1 h–1 µM−1), while A. fragilis had the highest Km (12.35 ± 0.71 µM) and Vmax (6.41 ± 0.23 µmol gDW–1 h–1), and A. fragilissima had the highest Vmax/Km (1.52 ± 0.26 µmol gDW–1 h–1 µM−1) and α (0.37 ± 0.01 µmol gDW–1 h–1 µM−1). Moreover, the PO4–3 uptake rate of the three species was faster at higher PO4–3 levels. These differences in species-specific nutrient uptake traits are likely caused by differences in morphology. These traits are important for survival and proliferation of this group of marine organisms, particularly in a nutrient-variable environment.
    This is contribution no. 494 from the University of the Philippines – the Marine Science Institute, (UP-MSI). We thank our laboratory aides Jerry Arboleda, Guillermo Valenzuela and Robert Valenzuela for their help in our sample collection. We also thank the UPMSI-Bolinao Marine Laboratory for providing us with the venue where we conducted our experiment and laboratory analyses. MYR acknowledges the Department of Science and Technology (DOST) Balik Scientist Program (BSP) fellowship.